Two hundred property folk turned out to mark the completion by Argent and Carlyle of the Piccadilly Place mixed-use development in central Manchester last night.

The party atmosphere reflected growing interest from occupiers in the impressive £100m scheme.

The first of two speculative office buildings, the 190,000 sq ft 3 Piccadilly Place is nearly 60% let and agents have terms out with three other parties that could take the majority of the remaining 80,000 sq ft.

James Evans, director at Savills, joint letting agents with GVA Grimley, said: "There is a strong possibility we will have further space under offer prior to Christmas."

The 110,000 sq ft 4 Piccadilly Place is fully available but agents said interest accelerated post-completion when the wraps came off recently.

Orega, the serviced office operator, opened a 12,500 sq ft centre on the eleventh floor of 3 Piccadilly Place on 1 October and is already 70% full. Orega will now take up the remaining 4,500 sq ft in its management agreement with building owner Carlyle on the ground floor sooner than expected.

Zach Douglas, director of Orega, added: "We will start fitting out the additional space before Christmas with a view to opening in February."

Douglas added that he is keen to open further centres in Manchester and Liverpool and is currently viewing buildings.

The ground floor restaurant and shop space at Piccadilly Place is also starting to let and Starbucks will take a corner site between the office and the residential phase.

The scheme, which took ten years from inception to practical completion, was anchored by a first phase pre-sale to City Inn and a new head office for freehold landowner Greater Manchester Passenger Transport Executive. The two speculative office buildings were forward-funded by private equity group Carlyle.

David Partridge, joint chief executive of developer Argent, said at the launch: "Piccadilly Place is not just for visitors to Manchester – the important thing for us is that it has become a community which is, in itself, a microcosm of everything that is great about this city. A mix of uses, combining offices with a hotel, apartments, shops and restaurants, directly accessible via our new bridge around stunning new public realm. It is this diversity, which makes it feel like a real piece of city, and which has moved it into the premier league of office, retail and residential locations within Manchester."

Letting agent James Evans added that the dwindling supply of Grade A office stock in the city would work in favour of 4 Piccadilly Place in 2010.

"A large occupier looking for 90,000 sq ft last year would have had quite a few options but that's not the case any more," said Evans. "Deals have split Belvedere House horizontally, 3 Hardman Street is all but fully let and that means there's precious little for a big occupier to move into going forward."

The scheme's closeness to Piccadilly Station has boosted its BREEAM 'Excellent' sustainability status and attracted public sector tenants in particular. The Equality and Human Rights Commission is the latest to be linked with Piccadilly Place.

The design and build team at Piccadilly Place included Carillion, Faithful & Gould, Hodder, Austin-Smith:Lord and Hoare Lee.